The invention relates to a process for producing bristle articles, in which the multifilament bristle strands, wound as endless material onto spools, are fed to a processing station, where the bristles, either in endless or cut to size form, are fixed to a bristle carrier; by a holding or tensile force acting thereon in timed sequence at the processing station and accompanied by the unwinding from the spools.
Soon after the appearnce of plastics which could be processed to fibres, such plastic fibres were also used for bristles, which were previously made from natural materials. The conventional procedure was initially used, in that the fibres were brought together to form multifilament strands and then cut, as required, to bundles (cf. e.g. DE-OS No. 28 48 510). The fixing of the bristle bundles to bristle carriers also initially took place in a conventional manner, e.g. on filling machines (DE-AS No. 1 049 823), in which the bundles, folded in a hairpin-like manner were inserted into prepared holes of the bristle carrier and were mechanically fixed by clips or the like. The plastic bristles could also be fixed to the bristle carrier by glueing, cementing, etc.
With the advance of plastic moulding technology, e.g. injection moulding, foaming of moulds, etc., it became possible to manufacture the bristle carriers inexpensively by such moulding processes, which also offered new possibilities for fixing the bristles to the bristle carrier, in that the bristles were introduced with their processing-side end into the mould of the bristle carrier and were fixed by moulding round (cf. e.g. German Pat. No. 845 933 and U.S. Pat. Nos. 2,643,158 and 3,408,112). Finally, numerous attempts were made to join the plastic bristles to the bristle carrier by two-sided plasticizing and shaping, as well as directly welding the plastic bristles to the bristle carrier.
After plastic bristles had been produced in endless or continuous manner and wound in endless strand form onto spools, it was obvious to carry out the processing to bristle products from the endless strand. Either the bristle fibres in connection with manufacture were brought together to form multifilament strands, wound onto storage reels and fed in multifilament strand form to the processing station (all the aforementioned publications), or in connection with the manufacture individual spools were wound, were removed from the storage reels at the processing machine, were combined into bundles and then joined to the bristle carrier (U.S. Pat. Nos. 2,710,774 and 2,035,709).
All the proposals made up to now in connection with the endless processing to bristle material have not been successful in practice. The starting point for all the difficulties has been the fact that a large number of bristles must be fixed to the bristle carrier with its small surface, so that when processing from the endless material a corresponding number of monofilaments must be removed from a corresponding number of storage reels and brought together in a very confined space, secured by clamping and fixing device and fixed in timed sequence to the bristle carriers. The problems can be solved to a certain extent if the bristle bundles are individually filled, because then the bundles can be successively fixed. However, this process is uneconomical. It can in particular not be used if the bristles are injection moulded or moulded into the carrier material or are fixed to the bristle carrier by welding. In such cases, all the bristles must be applied to the bristle carrier in one timed operating cycle. For example in the case of a scrubbing means with 100 bristle bundles of in each case 100 individual bristles, this would lead to 100,000 monofilaments and therefore 100,000 spools, which is neither technically, nor economically feasible.
If, in place thereof, multifilament bristle strands are processed, although the number of strands to be supplied and the number of storage reels can be produced, but in the case of the above example there would still be 100 reels, the processing difficulties would not be reduced for the following reasons. The bristle fibres obtained by spinning are stretched following the spinning machine to a multiple of the length, in order to straighten the molecular structure and give the fibres the necessary elasticity. This is generally followed by stabilization, which takes place at a relatively high temperature and is intended to fix the molecular structure, so that, during subsequent thermal stressing of the bristles, no changes take place. The thus stretched and stabilized fibres are then brought together to a multifilament strand and wound up. The individual fibres have different lengths, so that not all fibres have the same length within the bristle strand. In addition, the wound fibres change their behaviour by cold flow, because the generally shrink. Moreover, the cold flow does not take place in a uniform manner for all the fibres of a multifilament strand, so that length differences occur on the actual spool. If such a multifilament bristle strand is now removed from the storage reel, then the tension transfer only takes place via the shortest fibres, whereas other fibres form loops or hang in slack form and become tangled, which also leads to constant blockages on the processing machine. Furthermore, the plurality of spools, 100 in the above example, have different distances from the processing station, so that each bristle strand has a different transport path, so that the extent of loop formation differs for each bristle strand. In addition, length differences occur during the actual transportation or conveying, in that the bristle strands frequently have to be deflected several times. This leads to speed differences between the individual bristle strands and therefore to length differences between them. However, also the monofilaments of a multifilament bristle strand are subject to different forces during each deflection process, so that even within an individual strand length differences occur during processing.
Attempts have been made to eliminate loop formation (German Pat. No. 32 05 641), in that the bristle strand is twisted, so that the monofilaments are present in helical form within the strand. There is up to one twist per running metre. This was able to reduce loop formation, but not eliminate it. A further disadvantageous effect occurs through storing the bristle strands on spools. Due to the aforementioned cold flow characteristics of plastics and the lack of creep resistance, the individual fibres undergo deformation corresponding to the winding radius on the spool. However, in general the bristles must be absolutely linear to be able to fulfil their intended use. Through cross-winding of the strands (German Pat. No. 32 05 641) it has proved possible to keep the radius of curvature as small as possible. It is also known to eliminate the curvature after removal from the storage reel in that the strand is heated (DE-OS No. 2 849 510) or the bristle strands are passed through straightening rolls (U.S. Pat. No. 2,643,158). However, with none of the known measures has it been possible to exclude loop formation which is prejudicial to continuous processing.